Radiobiological effects of nitrogen ion implantation on upland cotton (Gossypium hirsutum L.) pollen grains

Abstract

To study the radiobiological effects of low-energy nitrogen ions on plant cells, nitrogen ions of various energies (10, 20 and 30 keV) were implanted into pollen grains of the upland cotton (Gossypium hirsutum L.) cultivar ‘Lumian 21’. The effects of irradiation on the pollen grains were assessed in terms of the ultrastructural changes in the exine and interior walls of the pollen grains, the germination rate, the number of pollen tubes in styles after pollination, the extent of the tip-focussed Ca2+ gradient and ultrastructural changes in F-actin in pollen tubes that developed from the treated pollen grains germinated in liquid medium. Nitrogen ions passed through the pollen grains by etching, penetrated the exine and interior walls, and destroyed cell structures in pollen grains. As the ion implantation energy increased, more pollen grains were destroyed, and the pollen grain germination rate and the number and length of pollen tubes decreased. Damaging effects were also observed with respect to the tip-focussed Ca2+ gradient and F-actin in pollen tubes. Treatment with 20- and 30-keV nitrogen ions caused the disappearance of the tip-focussed Ca2+ gradient in pollen tubes and affected the entire length of the tube. The function and structure of pollen tubes with respect to pollination and fertilisation may be affected by the changes in the ultrastructure of the pollen grains and the gene expression profile of pollen tubes after pollen grains are irradiated by nitrogen ions.